Exothermic insulating compositions comprising glass polishing residue

ABSTRACT

EXOTHERMIC INSULATING COMPOUND FOR USE IN THE CASTING OF METALLS COMPRISING 50-82% FINELY DIVIDED EFACTORY MATERIAL COMPRISING AT LEAST ABOUT 10% GLASS POLISHING RESIDUE, 0 TO 72% SAND, 0 TO 20% SILICA FLOUR, AND 0 TO 20% DIATOMACEOUS EARTH, 4-12% ASBESTOS FIBER, UP TO 12% CELLULOSIC MATERIAL, UP TO 12% REACTIVE METAL, UP TO 14% METAL OXIDE, AND 3-12% BINDER RESIN.

United States Patent Office 3,732,177 Patented May 8, 1973 3,732,177EXOTHERMIC INSULATING COMPOSITIONS COM- PRISING GLASS POLISHING RESIDUENorman F. Tisdale, Jr., Valencia, and James F. McCarthy, Mars, Pa.,assignors to The Union Commerce Bank, Cleveland, Ohio No Drawing.Continuation-impart of application Ser. No. 845,046, July 25, 1969. Thisapplication Mar. 27, 1970, Ser. No. 23,509 Int. Cl. B22c 1/22; C04b35/14; C08g 51/04, 51/18 U.S. Cl. 260-17.2 10 Claims ABSTRACT OF THEDISCLOSURE 'Exothermic insulating compound for use in the casting ofmetals comprising 50-82% finely divided refractory material comprisingat least about 10% glass polishing residue, to 72% sand, 0 to 20% silicaflour, and 0 to 20% diatomaceous earth, 412% asbestos fiber, up to 12%cellulosic material, up to 12% reactive metal, up to 14% metal oxide,and 3-12% binder resin.

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of application Ser. No. 845,046, filed July 25,1969, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to an exotherimcinsulating composition and' articles made therefrom and particularly toan insulating composition and an article for use as or in hot topsplaced on the top of ingot molds dun'ng ferrous metal ingot castingoperations.

In the ferrous metal industry, steels are normally melted in arefractory lined furnace and tapped into a ladle from which they areteemed into ingot molds for solidification into final ingots which arelater rolled, forged or otherwise worked into a final commercial shape.During the solidification of ingots, the metal freezes in the ingot moldfrom the bottom upwardly and from the sidewalls toward the centerleaving a generally central conical portion which hardens last or formsa pipe and into which impurities which may be present in the moltenmetal are concentrated by segregation or freeze separation. In order toeliminate or to reduce substantially this piping and segregationcharacteristic in the freezing of ingots, it is the practice to place ahot top in the form of a wall or dam around and above the opening in thetop of the ingot mold to provide a reservoir for molten metal. A hot topmay be prepared from metal or a refractory material or combinations ofboth and generally is insulated, at least in part, to cause a pool orreservoir of the molten metal to remain molten after the pouring anduntil a major portion of the ingot has solidified. The pool or reservoirpermits molten metal to fill the forming central conical portion of theingot to eliminate the pipe and to force segregating impurities to thehot top section of the ingot. After solidification, the portion of theingot within the hot top many be removed readily by cropping to providean ingot more uniform in composition and substantially void free for theperformance of further work on the ingot. In this manner, many of theproblems in rolling, forging and other finishing operations which arecaused by non-uniform ingots are eliminated.

Many compositions have been proposed for hot tops, or for insulating atleast the inner surfaces of a hot top, to overcome the characteristicdifficulties of prior art materials which include too rapid heat loss,contamination of the ingot and others. Also, many of the premoldedinsulating materials or panels which are used for insertion asinsulating surfaces inside hot tops are very fragile and are readilybroken. Known premolded materials generally have little or nodeformability to permit use in non-uniform hot tops and are diflicult tostore and handle prior to use. Although some of these materials have metwith a measure of commercial success, prior art premolded insulatinginserts for hot tops have not been a complete answer to the problems.

To perform most satisfactorily, premolded insulating inserts for hottops, or hot tops prepared at least in part from molded insulatingcompositions, should have good resistance tobreakage at atmospherictemperatures to permit good storage and handling; should have a measureof deformability to permit use in non-uniform applications; should havegood insulating and a measure of exothermic properties to permit minimumheat loss from the reservoir of molten metal; should break down or losestructural integrity after use without contaminating the ingot to bereadily removable and disposable from the ingot and hot top; and shouldbe a low cost item to permit economy of operation. Additionally it ismost desirable that the compositions process easily and rapidly intoliners and panels. It is clear, therefore, that the composition andarticle of this invention which meet these requirements are worthwhileadvance in the art.

SUMMARY OF THE INVENTION In accordance with this invention, a new andnovel composition and article are disclosed which eliminate the priorart problems. The composition has excellent insulating and exothermicproperties; and when molded into shapes or forms, parts are obtainedwhich are very resistant to cracking and spalling. Insulating partsmolded from the composition have considerable deformability andresilience at ordinary temperatures which provide good resistance tobreakage and damage during handling and storage. The molded compositionhas the quality of breaking down substantially completely after useWithout contamination of the poured ingot to permit easy separation andremoval from an ingot and a hot top, when used. The compositions processeasily and rapidly with resultant economies in time and cost.Additionally, improved insulation properties are obtained with overallreduced composition cost.

In accordance with this invention, a composition is provided having thefollowing parts by weight:

50-82% of finely divided refractory material, 4-l2% asbestos fiber,

012% of a cellulosic material,

012% of a powdered reactive metal,

0-14% of metal oxide, and

312% of a binder resin.

refractory material comprises about 60-79% by weight of the totalcomposition; the glass polishing residue comprises at least about 15%,and the finely-divided sand comprises 0 to 64%. The diatomaceous earthmay be any of those well known in the art. It is preferred that thefinely-divided refractory material have a particle size in a range below60 mesh, preferably below 70 mesh, i.e., less than 0.25 mm.

The glass polishing residue, which results from glass polishingoperations well known in the art, contributes several importantadvantages to the composition. It imparts equal or better insulatingproperties at particle sizes substantially larger, tag. 60 or 70, thanthe very fine particle sizes, e.g. 200 mesh, generally required toobtain optimum insulation with materials such as finelydivided sand,silica flour, and the like. As a general rule greater porosity and,therefore, better insulation is achieved with smaller particle sizerefractory materials. The glass polishing residue with a larger particlesize range imparts as good or better insulation properties without thedisadvantages of greatly reduced filtration rates normally caused bysmaller particle size refractory additives. Thus processing of theexothermic insulating compositions is considerably easier, faster, andmore economical. Binder requirement for a given weight percent ofrefractory mix is also reduced by smaller over-all surface area of thelarger particle sizes with resulting economies. In addition to excellentinsulation capacity, other physical properties of the finished productare superior including resistance to cracking and spalling, resilience,resistance to breakage and damage during handling and storage, anddisintegration after use.

The asbestos fiber may be any of the well known asbestos fibermaterials, either substantially solid or tubular, and the length offibers used is not critical to the invention. Any of the shorter-length,more economical fibers may be used as is desired.

The cellulosic material may be at least one of any of the Well knowncellulosic materials such as Wood flour, ground-wood, pulp, shreddedpaper and like materials and of these it is preferred that wood flour beused.

The powdered reactive metal may be at least one selected from the groupconsisting of reactive metals, alloys of reactive metals, and mixturesthereof. Metals and alloys in this group comprise aluminum, boron,aluminum-silicon, boron-silicon, calcium-silicon, ferro-silicon,ferro-silicon-aluminum, and of these, aluminum, aluminum-silicon andcalcium-silicon are most preferred. The particle size of the powderedreactive metal is not critical: however, for good distribution withinthe composition of this invention it is preferred that the particle sizeapproximate that of the finely divided refractory material.

The metal oxide of this invention may be any metal oxide is compatiblewith the other components of a composition, exothermically reactive withthe reactive metal at the teeming temperatures, of the molten metalbeing cast, and substantially non-reactive at mixing, storage andhandling conditions of the exothermic insulating compositions. Thosemetal oxides which are preferred are manganese dioxide, iron oxides andmixtures thereof.

The binder resin may be any of the well known binder materials such asthe silicates, polymers such as phenol formaldehyde, urea formaldehyde,polyvinylacetate, furfuryl alcohol, combinations thereof and mixturesthereof. As is Well known, adjustment of the pH of solutions of thecompositions of this invention by the use of additives may be necessaryor desirable to promote or effect the cure of the binder resin to adherethe composition in a desired shape or form.

After mixing of the desired compounds in any convenient order insuitable mixing apparatus with a carrier such as water or other, ifdesired, the composition of this invention 'may be formed into a desiredshape for a hot top, an insulating panel, other insulating article andthen dried and heated, if necessary, to cure the resin binder used toadhere the mixture.

When an insulating composition is to be used as a hot top, or a part ofa hot top, suitable reinforcing such as metal, fiberglass or plasticscreen, cloth or fibers may be incorporated into the article as is wellknown in the art. Also, when metal or ceramic hot tops are used, acomposition may be prepared in a paste or slurry form for coatingdesired areas of the hot top or ingot mold prior to the curing of thebinder.

The invention may be understood best by reference to the followingexamples illustrating the composition as disclosed previously in variousforms and embodiments. All parts are parts by weight unless otherspecified.

EXAMPLE I A composition made up of 65 parts of finely divided glasspolishing residue from a glass polishing operation, 5 parts wood flour,8 parts of asbestos fiber, 8 parts of powdered aluminum, 9 parts ofmanganese dioxide and 7 parts of phenol formaldehyde was mixedthoroughly with sufiicient water to form a slurry having 15% by weightsolids. Sufficient of the mixed slurry composition was added to a moldto form a rectangular hot top 12 inches square and 10 inches high and amajor portion of the water was removed from the slurry by pressure. TheWet molded composition was removed from the mold and cured at atemperature of 380 F. for 2 hours 15 minutes. The prepared hot top wasused under ordinary teeming operating conditions and performedeffectively both for insulation and resistance to breakage.

A portion of the prepared composition was molded also into a test paneland tested for its insulating properties. It Was found to have aninsulating K value of under 1.7 at 2500 F.

EXAMPLE II A composition having the following components was prepared:

Parts Glass polishing residue 63 Wood fiour 7 Powdered Ca-Si 6 M1102 9Asbestos fiber 8 Phenol formaldehyde 7 Suificient water to form a slurrycontaining 13 to 20% by weight solids was added and the mixture formedinto a hot top as in Example I. The hot top performed effectively andits K value was under 1.7 at 2500 F.

EXAMPLE III A hot top was formed as in Example I from the followingcomposition:

Parts Glass polishing residue 63 Wood flour 6 Ferro-silicon-aluminum 6M1102 9 Asbestos fiber 9 'Phenol formaldehyde 7 Water to form a slurrycontaining 13 to 20% by weight solids.

The hot top performed effectively and its K value was essentially thesame as Example I.

EXAMPLE IV A hot top was formed as in Example I from the followingcomposition:

Water to form a 15 by weight solids slurry.

The resulting hot top performed effectively and had a K factorsubstantially identical to that of Example I.

EXAMPLE V A composition identical with Example I was prepared exceptthat the resin binder was made up of Parts Phenol formaldehyde (powered)4 Polyvinylacetate (powered) 3 A hot top was formed as in Example I andits K value found to be substantially identical with Example I.

EXAMPLE VI A hot top was formed as in Example I having the fo1- A lowingcomposition:

The mixture was added to water to form a slurry of 20% by weight solidsand the pH adjusted to 5 to 5.5 with sodium bisulfate. The resulting Kfactor was substantially the same as that of Example I.

EXAMPLE VII A hot top of the same composition as Example I was formedsubstituting for phenol formaldehyde a like amount of furfurylalcohol-urea formaldehyde resin mixture. Again, the product had a Kfactor substantially the same as Example I.

Although certain preferred embodiments of this invention have beenillustrated and described in the foregoing description, it will beunderstood that this invention is not limited to the preferredembodiments and may be embodied otherwise within the scope of thefollowing claims.

We claim:

1. A composition for insulating metal castings consisting essentially byweight of about 50-82% finely-divided refractory material comprising atleast about glass polishing residue, 0 to about 72% sand, 0 to about 20%silica flour, and 0 to about 20% diatomaceous earth; about 4-12%asbestos fiber; 0 to about 12% cellulosic material; 0 to about 12% offinely-divided reactive metal; 0 to 14% of metal oxide exothermicallyreactive with said reactive metal at the teeming temperature of themetal casting; and about 312% of a binder resin.

2. The composition of claim 1 wherein the refractory material has amaximum particle size of about 60 mesh.

3. The composition of claim 1 wherein the refractory material is about60-79% and comprises at least about 15% glass polishing residue, 0 toabout 64% sand, 0 to about 20% silica fiour, and 0 to about 20%diatomaceous earth.

4. The composition of claim 3 wherein the refractory material has amaximum particle size of mesh.

5. The composition of claim 1 wherein the reactive metal is aluminum,aluminum-silicon, calcium-silicon, or mixtures thereof.

6. The composition of claim 4 wherein the reactive metal is aluminum,aluminum-silicon, calcium-silicon, or mixtures thereof.

7. The composition of claim 5 wherein the metal oxide is manganesedioxide, iron oxide, or mixtures thereof.

8. The composition of claim 6 wherein the metal oxide is manganesedioxide, iron oxide, or mixtures thereof.

9. The composition of claim 1 wherein the binder resin is phenolformaldehyde, urea formaldehyde, furfuryl alcohol, polyvinylacetate,furfuryl alcohol-urea formaldehyde, furfuryl alcohol-phenol formaldehydeor mixtures thereof.

10. The composition of claim 4 wherein the binder resin is phenolformaldehyde, urea formaldehyde, furfuryl alcohol, polyvinylacetate,furfuryl alcohol-urea formaldehyde, furfuryl alcohol-phenol formaldehydeor mixtures thereof.

References Cited UNITED STATES PATENTS 3,123,878 3/1964 Davidsonl0638.22 3,300,322 1/1967 DeGeer 1-0638.35 2,798,818 7/1957 Pletsch etal 10638.2 3,230,056

1/1966 Arant et al 106-3822 OTHER REFERENCES E. WOODBERRY, AssistantExaminer US. Cl. X.R.

